Phase issues

[Davenhurst]

I've been going through some of the posts here, and a piece of advice that often crops up is to "check for phase issues". I understand the physics involved and the issues presented and also how to overcome it, but I don't quite understand how to know that there is a phase issue in the first place, other than listening and experimenting. What signs am I looking/listening out for? Is there some sort of definite way of pin-pointing a phase problem? I use Cubase SX with Waves plugins, the Waves PAZ Analyzer shows me a phase reading, with occasional peaks falling into the "anti-phase" region. Should this bother me?

What about situations like having two mics on a guitar amp? I've worked out that if you mic a snare drum top and bottom you need to put one out of phase. That makes perfect sense. Maybe I'm reading too much into it, and I know experience will count for a lot but maybe one of you guys knows a resource that explains it. (I know, google search - I'm on it - friendly advice is always gratefully received though).

Ta.

 

[bennychico11]

https://homerecording.com/bbs/showthread.php?t=200512

Take a look at the second page, second post down. I give some examples (which I believe are still all available on their respective sites)

Basically anytime you use two mics on a single source you need to check for phase issues. Phase is something that just happens around us and is not always a bad thing. When it starts to take away from frequencies (comb filter) too much...that is when we try and step in and correct it.

I always suggest actually physically moving the track that has the 'delayed' microphone. This will more often than not correct the problem....at least when talking about two microphones facing the source. When we're talking about the snare mics, this is a little different because of their physical location in reference to the snare. In that case I'd just use the polarity button.
The polarity button can also help at times with two mics on a guitar, but remember this just flips our wave form around and we may still get undesirable comb filtering since the waves were actually delayed and not just 180 degrees off axis from eachother.

But basically, phase problems you should be able to hear and SEE in software program. Examples given in the link above. Also in that link I talk about how you can experiment on your own with a copy of the same track. When played together, the two tracks just sound louder. Slowly nudge the copy a few samples at a time and listen to what's happening between the two. You start to hear some weird swirling sound and it'll start to annoy you. That's bad phasing! Continue nudging further and it'll start to sound like a delay rather than a phase problem.

 

[Davenhurst]

Cool, thanks. As I say, I understand the physics of it - e.g. playing two identical waves while putting one out of phase will (or should) produce silence. A-level physics took care of that, but it's applying it to a recording situation that sometimes stumps me. Your reply = v. helpful.